128 A. RICHARDS. 



scarce y possible that Moniezia differs from the majority of 

 other forms in the amitotic multiplication of nuclei." There are, 

 however, a considerable number of differences in the results ob- 

 tained in the two allied forms, differences which I hope to make 

 clear in the course of this discussion. 



Spengel in 1905 before the Deutsche Zoologische Gesellschaft 1 

 stated that neither mitotic nor amitotic cell division had been 

 observed in cestode development. 



C. v. Janicki ('07) in an important paper upon the embryonic 

 development of T&nia serrata states that he finds no pronounced 

 division figures up to the growth period of the oogonia, but 

 during the growth period he describes spiremes; he does not 

 suggest amitosis as the explanation of his failure to find mitoses 

 but merely says that the divisions must have passed very quickly. 

 In the cleavage stages achromatic parts of the division figures 

 are often hard to demonstrate. 



In so far as it touches the same points my own work ('09) on 

 this form agrees with that of v. Janicki. I recorded my failure 

 to find amitosis and noted that mitoses are more infrequent than 

 one would expect. 



In 1908 appeared the paper by Young upon the histogenesis 

 of Cysticercus pisiformis, the cysticerus stage of Tcenia serrata. 

 This paper is revolutionary indeed, and agrees in practically no 

 cytological points with the work of v. Janicki and myself. Not 

 only does he accept Child's conclusions and their bearing upon 

 hereditary problems but he refuses to subscribe to Virchow's 

 dictum "omnis cellula e cellula." He believes that nuclei arise 

 de novo in accordance with a tentative hypothesis, of which his 

 statement is as follows: "I believe that the nucleus in these 

 forms is not a morphological but a physiological entity; that the 

 nuclear granules are fundamentally the same as the remaining 

 protoplasm of the cell, but are differentiated therefrom under 

 physiological conditions which w r e do not at present understand ; 

 that these granules are perhaps reserve material stored up in the 

 nucleus for future use, the entire cell body being occasionally 

 converted into a nucleus; and that the nucleus varies in structure 

 from time to time in response to the varying physiological de- 



Child, 'o^a, p. 277. 



